1. Field of the Invention
The present invention relates to a method of supplying an etching gas and an etching apparatus.
2. Description of the Related Art
In general, in a gas supply system for a semiconductor manufacturing apparatus, a plurality of gases are output from a gas box provided outside the apparatus, are joined together in one common pipe (manifold) through a plurality of individual gas supply lines, and are guided into a processing container of the semiconductor manufacturing apparatus.
When gas species are switched in the same apparatus, attempts have been made to prevent the switching from adversely affecting processes before and after the switching. For example, an attempt to perform a stable step for about 5 seconds before performing a process after switching has been suggested. By performing the stable step, stability of the process after the switching can be achieved. Also, accordingly, since hunting (overshoot) in a gas flow rate which occurs at an initial stage when a valve of a mass flow controller (MFC) is controlled to change from a closed state to an opened state occurs in the stable step, the hunting is prevented from adversely affecting the process after the switching.
Patent Document 1 and Patent Document 2 disclose technologies of controlling gases when an etching process and a film formation process are switched therebetween. For example, Patent Document 1 involves providing a transition process including both an etching gas and a deposition gas while the etching gas and the deposition gas are switched therebetween and thus reducing discontinuity of gas species during the switching. Patent Document 2 involves, when the etching gas and the deposition gas are switched therebetween, controlling flow rates of an etching gas and a deposition gas by using MFCs respectively attached to gas supply lines, further controlling a total flow rate of a gas mixture of the etching gas and the deposition gas by using an MFC attached to a common pipe, and supplying the gas mixture into a processing container.
However, Patent Documents 1 and 2 fail to disclose a method of supplying a gas, where a flow rate of a gas is stably controlled by preventing hunting in a gas flow rate which occurs when a gas is switched.
[Patent Document 1] Japanese Laid-Open Patent Publication No. Hei 11-195641
[Patent Document 2] Japanese Laid-Open Patent Publication No. 2000-306887